This invention relates to a bulky composite sheet comprised of continuous fibers or filaments and, more particularly, to such a composite sheet suitably used to wipe up dust and dirt on floors, walls, windows, and the like.
In the accompanying drawings, FIGS. 8 and 9 are perspective views of composite sheets 101 comprising a base sheet, for example, made of a nonwoven fabric and continuous fibers heat-bonded with the base sheet and FIG. 10 is a perspective view of a holder 103 by which the composite sheet is held. These composite sheets 101 and holder 103 are described in Japanese Patent Application Laid-open No. 1997-149873. Floors can be wiped by the composite sheet 101 with the holder 103 in a user""s hands to collect dust and dirt by the upper surface of the composite sheet 101. In this known composite sheet 101, a multiplicity of continuous fibers 108 are heat-bonded integrally with the base sheet 107 along attaching lines 105. Such a composite sheet 101 is made by placing the continuous fibers 108 upon the base sheet 107 and feeding them into a gap between a pair of heated rolls for embossing. As will be apparent from FIG. 8, crossings 131 of the attaching lines 105 are numerous in the composite sheet 101, and, therefore, the continuous fibers 108 disadvantageously tend to be unevenly distributed in the vicinity of these crossings 131 during an embossing process.
In the case of the composite sheet 101 as illustrated by FIG. 9, the continuous fibers 108 tend to shift transversely along an arrow Q toward a side edge of the base sheet 107 as the continuous fibers 108 and the base sheet 107 are fed in the direction as indicated by an arrow P to the pair of embossing rolls. Consequently, it is difficult to evenly distribute the continuous fibers 108 transversely of the base sheet 107.
An object of this invention is to provide a bulky composite sheet and a method for making such a composite sheet.
According to one aspect of this invention, there is provided a composite sheet having a longitudinal axis, the composite sheet comprising a base layer having upper and lower surfaces and a surface layer comprised of continuous fibers extending along the longitudinal axis and having a predetermined width defined between transversely opposite side edges of the surface layer extending along the longitudinal axis and attached to at least one of the upper and lower surfaces of the base layer by a plurality of attaching lines extending in a direction intersecting the longitudinal axis.
In such a composite sheet, the attaching lines comprise a plurality of first attaching lines extending at intervals in one half region of the surface layer defined on one side of the longitudinal axis extending so as to bisecting the width of the surface layer and a plurality of second attaching lines extending also at intervals in the other half region of the surface layer on the other side of the longitudinal axis. The first and second attaching lines extend obliquely to the longitudinal axis so as to intersect each other on extensions of the first and second attaching lines toward the longitudinal axis.
According to another aspect of this invention, there is provided a method for making a composite sheet having a longitudinal axis, the composite sheet comprising the steps of continuously feeding a base layer web having upper and lower surfaces and a surface layer web comprised of continuous fibers extending along the longitudinal axis and having a predetermined width defined between transversely opposite side edges of the surface layer extending along the longitudinal axis, placing the surface layer web upon at least one surface of the base layer web and attaching the surface layer web to the base layer web along a plurality of attaching lines extending in a direction intersecting the longitudinal axis.
In such a method, this invention further comprises the steps of deregistering and spreading a continuous fiber tow for the surface layer web to the predetermined width on the one surface of the base layer web and providing a plurality of first attaching lines extending at intervals in one half region of the surface layer web defined on one side of the longitudinal axis bisecting the width of the surface layer web and a plurality of second attaching lines extending also at intervals on the other half region of the surface layer web defined on the other side of the longitudinal axis so as to make the first and second attaching lines extend obliquely to the longitudinal axis and intersect each other on extensions of the first and second attaching lines toward the longitudinal axis, wherein the first and second attaching lines are successively formed from the longitudinal axis toward transversely opposite side edges of the surface layer web as the base layer web and the surface layer web are fed in the longitudinal axis.